Vulkan support doesn't mean a GPU is powerful. It's just a graphics API.

That may be true in about 5 years. And it's true on a very strictly literal level, but that's it.

But for now, you need a pretty powerful GPU to support Vulkan, mostly on the count that it's a very new API and support was only written for GPU's that are still somewhat recent and still under manufacturer support. Naturally, that's more powerful GPU's, because most manufacturers will not bother writing proper drivers for something that is too old.

So by deductive reasoning, he's partially correct, he just got the presumption wrong that you'd need around a GTX 1080 to support it, which you do not.

New does not mean powerful. My Intel HD Graphics 630 is recent enough to support Vulkan, but shits itself if you simply turn SSAO on in GZDoom.It also shits itself if you try to run Skyrim at decent looking settings.It also shits itself if you try to run anything very recent in general.

It's literally the opposite of a powerful GPU, and yet, it supports Vulkan. So no, he's not even partially correct.

My Intel UHD Graphics 620 officially supports Vulkan too, but given the reputation of the drivers I first will have to wait and see if a future GZDoom will run on my machine without problems with a Vulkan renderer...

The lowest Vulkan compatible graphics cards around would be too slow to run any advanced postprocessing. But that's not the point of Vulkan. The point is to allow using some multithreaded processing on the CPU side. Even with my old Geforce 550Ti which these days would rank a bit better than modern low end Intel it was mainly the CPU being the bottleneck. In addition, for AMD and Intel the drivers were another major bottleneck. So even for such cards Vulkan should provide a decent speedup on complex maps if everything works out as intended.

What these 67% mean is that those people run a somewhat recent - maximum 5 years old - graphics card. If you add another 17% who run stuff from 2011 or 2012 it should give a bit of perspective how old the stuff is that is being considered to be dropped.

For Vulkan, GPUs as far back as Kepler (GeForce 650 and higher) and 1st gen GCN (AMD 7700 series and higher) support it. Intel iGPUs support it since Skylake.

I know for Doom 2016 Vulkan greatly benefits AMD GPUs while on nVidia the gains are more modest if there are any at all. Would this be the case for GZDoom as well? (yeah, I know it's apples and oranges, but it's the only game I know of with both OpenGL and Vulkan renderers)

It should benefit everyone greatly if all goes well - a Vulkan renderer would allow multi-threading, which will free up some (or even a lot of) CPU time in the renderer, as any (single-threaded) hardware renderer for Doom is CPU-bound due to (AFAIK) the BSP.This would also make maps with absurd linedef or sector counts run faster, I believe.

AMD will profit more because its driver overhead in OpenGL is larger.The main benefit will be the ability to multithread the scene generation and maybe later to preconstruct complete render lists for entire sectors. And this part will be hardware independent. In a single threaded scenario it is very unlikely that NVidia would benefit at all because their driver overhead is virtually non-existent.

I don't think that supporting Vulkan will accelerate grasphics card upgrades. Most people do that when it becomes necessary, either because their old card becomes too weak or the entire computer needs to be replaced.

As for XP, the only point is that as of right now, supporting it or dropping it is a wash. We wouldn't gain anything by removing XP support. I guess it will be removed along with 32 bit support overall. As of yesterday, XP user share was 0.3% and 32 bit user share was 3% and with 32 bit user share rapidly declining (6% to 3% over 4 months) this is going to end rather sooner than later.

Does this means that 67% from 2000 gzdoom users, ~1300 people, have videocard from the level of gtx1080?

A bit more detail here:

I did a bit of number crunching of the current results from 11000 users.

Roughly one third (3700 of 11200 to be precise) runs a modern NVidia card which is fast enough to have all postprocessing effects enabled.Another 900 uses an older but still Vulkan compatible NVidia card that is at least fast enough to run the game at full HD resolution with postprocessing disaabled but otherwise full speed.

I haven't done more yet, this is a preliminary result of checking roughly 5000 reports of Vulkan compatbile NVidia hardware.